Our long-term objectives on this project are to explore the molecular biology of membranes, to provide molecular mechanisms for the processes of active transport through membranes, the mechanochemistry of membranes, and cell activation of hormones, mitogens, and other ligands. We propose to carry out the following specific studies: 1) to investigate a molecular mechanism of active transport, the "aggregate-rearrangement" mechanism, using the Ca-ATPase transport protein of sarcoplasmic reticulum membranes. Fluorescence probes will be covalently attached to the protein both in intact membranes and in the isolated state. The latter will be reconstituted in synthetic lipid vesicles. In both cases, the probes will be used to monitor the postulated rearrangements occurring in transport. 2) to study the localization of a new smooth-muscle protein, filamin, in non-muscle cells, and its role in mechanochemical processes of these cells; 3) to develop methods of improving ultrastructural cytochemistry through the use of ultrathin sections prepared by ultracryotomy. BIBLIOGRAPHIC REFERENCES: An experiment eliminating the rotating carrier mechanism for the active transport of Ca ion in sarcoplasmic reticulum membranes, Anne Dutton, E.D. Rees, and S.J. Singer, Proc. Nat. Acad. Sci. U.S.A. 73:1532 (1976). Equilibrium and kinetic effects of drugs on the shapes of human erythrocytes, Michael P. Sheetz and S.J. Singer, J. Cell Biol. 70:247 (1976).